Descreened OEM MAF

04crewvt · Post by **04crewvt** » Sun Oct 23, 2005 5:17 am

Ok so I just had to try something that a lot of you have talked about for a freebee mod. Having a auto x-ray scan tool I felt that it would be best to go about this scientifically so i scanned computer just before doing the mod, saved the data and then removed the screen and tested again. Total lapsed time between scan apx 15 minutes absolutely no other changes to vehicle between scans.
Here is what i got:
Initial- air flow rate 1.72 lb/minute short term fuel trim 1 -10.2% short term fuel trim 2 -10.2% MAP 12.00 ignition timing advance 6.5
Modified- air flow rate 2.01lb/min short term fuel trim 1 -4.00% short term fuel trim 2 -4.00% Map 13.00 ignition timing advance -1.0
overall 17% increase of air flow rate for 10 min work
Not bad at all if i do say so myself. I will have to run it for a couple of days and rescan to see what changes the computer makes to its programing and let you know what I find.

chumley · Post by **chumley** » Sun Oct 30, 2005 1:16 am

Any news??

04crewvt · Post by **04crewvt** » Sun Oct 30, 2005 7:43 am

Test results so far.
Ok I pulled the screen and posted the numbers last week. Before I drove the truck I pulled both ECM fuses to reset to baseline programming. I have only put apx 50mi on this past week and so far no SES light or other drivability problems.I just completed a scan a few minutes ago the results are as follows.
air flow rate- 1.95 lb/min short term fuel trim 1 -8.6% short term fuel trim 2 -8.6% Map 13 ignition timing advance 8.50 So far all the long term fuel trim numbers remain at -4.00

Subjectively, the truck does seem to bog less in corners when you have slowed down and then reaccelerated, less lag before power comes back, but from an engine point of view it looks like the slight overall difference in the air flow is more than compensated for by the ECM. My guess is the factory programming has more than enough leeway just to cope with different altitudes/barometric pressure that there appears that this mod will do no harm but probably won't give much real world benefit either.
Oh well,I will keep you posted when I put a few highway miles on.That may make some more long term changes show up.

PS - Since winter temperatures arrived this week the truck has been running in lower temps than the week before I did the mod. Not sure if that will make any long term difference but wanted that variable put in there as well.

04crewvt · Post by **04crewvt** » Thu Nov 24, 2005 6:06 am

Well with cold weather finally here I can say that there definitly seems to be a bit less lag when slowing down and then accelerating into a turn. Hesitation is much less. No real gas milage or horsepower effect see just runs a little smoother.

Post by **HenryJ** » Thu Nov 24, 2005 6:16 am

What are you running for an intake and filter system?

I have been running descreened for years. I did make the change with a modified airbox, and since then I have been running the K&N FIPK.

04crewvt · Post by **04crewvt** » Thu Nov 24, 2005 6:21 am

Backyard Air system from E-Bay

Post by **HenryJ** » Thu Nov 24, 2005 6:39 am

One of the arguments in favor of the screen is that it is designed to straighten, or smooth the air flow over the sensors. The stock airbox is reported to be very turbulent.
By changing the intake the benefits of this may be reduced.
It does also serve to protect the sensors, however that is a weak argument since the airfilter does that.

I too have not seen any detrimental effects from descreening.